Molecular configuration and interactions of the amide group. Part 4.—Band contour analysis of the infra-red spectrum of N-methylformamide in the vapour phase at 20°C

Abstract

The infra-red spectrum of N-methylformamide vapour at 20°C has been obtained using a 40 m pathlength cell. Comparison of the observed PR separations of band envelopes with those predicted for the cis and trans models using the methods of Badger and Zumwalt, and Seth Paul and Dijkstra, suggest that the molecule is predominantly in the trans conformation. The spectrum of N-methyl-acetamide vapour (T= 20°C; l= 40 m) is also reported but does not allow differentiation between trans and cis isomers.